This invention relates to a disposable undergarment such as a disposable diaper or a diaper cover.
Japanese Patent Application Publication No. 1998-328237A describes a disposable undergarment composed, in its longitudinal direction, of front and rear waist regions and a crotch region extending between these waist regions wherein a pair of wings made of stretchable sheet material extend outward from transversely opposite side edge portions of the rear waist region in a transverse direction of the undergarment and lateral ends of the respective wings are made of elastic material presenting a stretch stress higher than that in the remaining portions. The undergarment disclosed in the Publication comprises a liquid-pervious topsheet, a liquid-impervious backsheet and a liquid-absorbent core disposed between these sheets. Tape fasteners serving to connect the front and rear waist regions are attached to free side edge portions of the respective wings. To put the undergarment on a wearer""s body, the wings are stretched in a waist-surrounding direction to engage the tape fasteners with a target tape strip attached to the front waist region and thereby to connect the front and rear waist regions to each other. With the undergarment, the transversely opposite side edge portions of the undergarment in its crotch region are pulled in a thigh-surrounding direction as the wings are stretched in the waist-surrounding direction. In this way, the transversely opposite side edge portions ensure the undergarment to be tightly held around the wearer""s thighs.
Depending on a circumferential size of the wearer""s thigh, it is sometimes desired for the undergarment such as a disposable diaper or a diaper cover to alleviate a compressive effect of the transversely opposite side edge portions in the crotch region around the wearer""s thighs. In the case of the undergarment disclosed in the Publication, this may be achieved by connecting the front and rear waist regions to each other without fully stretching the wings in the waist-surrounding direction. However, this will result in that the undergarment can not be reliably held around the wearer""s waist and the undergarment is apt to get out of its proper position.
It is an object of this invention to provide a disposable undergarment that can be reliably held around a wearer""s waist to prevent the undergarment from slipping down without excessively compressing the wearer""s thighs.
According to this invention, there is provided a disposable undergarment contoured by transversely opposite side edge portions extending in a longitudinal direction and longitudinally opposite end portions extending in a transverse direction so as to be composed, in the longitudinal direction, of a front waist region, a rear waist region and a crotch region extending between these waist regions, the undergarment having a pair of elastically stretchable first wings extending outward from transversely opposite side edge portions of the front waist region and/or the rear waist region, the first wings having first proximal side edge portions lying on the transversely opposite side edge portions of the waist region and first free side edge portions spaced outward from the first proximal side edge portions in the transverse direction, the first free side edge portions being provided with means to connect the front and rear waist regions to each other wherein the first proximal side edge portions are contiguous to the transversely opposite side edge portions of the crotch region and a stretch stress generated in the first wings as the front and rear waist regions are connected to each other is exerted upon the undergarment in a waist-surrounding direction as well as in a thigh-surrounding direction.
According to this invention a pair of elastically stretchable second wings prepared separately of the undergarment extend outward from the transversely opposite side edge portions of the waist region in the transverse direction so as to be placed upon the first wings, the second wings having second proximal side edge portions lying on the transversely opposite side edge portions of the waist region and second free side edge portions spaced outward from the first proximal side edge portions in the transverse direction and fixed to the first free side edge portions, wherein the second proximal side edge portions are not contiguous to the transversely opposite side edge portions of the crotch region and a stretch stress generated in the second wings as the front and rear waist regions are connected to each other is exerted upon the undergarment in a waist-surrounding direction.
According to one embodiment of this invention, a transverse dimension of the first wing as measured from its first proximal side edge portion to its free side edge portion and a transverse dimension of the second wing as measured from its second proximal side edge portion to its second free side edge portion are in a relationship of the first wing being nearly equal to the second wing or the first wing being greater than the second wing and wherein values of the stretch stress generated in the first and second wings as these first and second wings are stretched outward in the transverse direction are in a relationship of the first wing being less than the second wing.